Idle Reduction

Why is idle reduction important? What are ways that I can prevent idling, and what are the benefits of doing so?

Idling, the time when a vehicle’s engine is on but the vehicle is not moving, wastes over 6 billion gallons of fuel each year in the United States according to Argonne National Laboratory (ANL). This adds up to more than $20 billion annually in fuel costs. For example, heavy-duty trucks frequently idle at rest stops; an estimated 650,000 long-haul trucks use more than 685 million gallons of fuel per year by unnecessary idling. Idle reduction technologies and practices can help lower fuel consumption and fuel costs, protect public health and the environment, and increase U.S. energy security. Reducing idle time can also help reduce engine wear and maintenance costs. Finally, idling for long periods is illegal in many states and jurisdictions.

Idle Reduction Technologies and Practices

Heavy-Duty Vehicles

Truck stop electrification and onboard equipment can help reduce idling at truck stops, roadsides, and delivery sites. It is important to note that the cost-effectiveness of the technologies below depend on the vehicle applications and climates in which they are used as well as the duration of the idling.

Truck Stop Electrification provides power from an external source for important systems such as air conditioning, heating, and appliances without needing to idle the engine during required stops at rest areas.

Auxiliary Power Units are portable units that are mounted to the vehicle, and provide power for climate control and electrical devices in trucks, locomotives, and marine vehicles without idling the primary vehicle engine.

Energy Recovery Systems use the vehicle’s heat-transfer system to keep the truck’s heater operating after the engine is turned off, using engine heat that would otherwise dissipate.

Automatic Engine Stop-Start Controls sense the temperature in the sleeper cabin and automatically turn the engine on if the sleeper is too hot or too cold.

Cab or Bunk Heaters supply warm air to the cab or bunk compartment using small diesel heaters. Heaters can be coupled with air conditioners if needed.

School Buses

School bus idling is particularly problematic because of the negative health impacts for children. School bus engines should be turned off while the engine is not needed, such as at loading and unloading areas, and should only be turned back on when the bus is ready to depart. Idle reduction technologies for school buses that operate in cold climates include small on-board diesel cabin heaters and electrical block heaters, which can provide warming for the passenger compartment and engine.

Light- and Medium-Duty Vehicles

For light-and medium-duty vehicles, the primary idle reduction strategy is to turn the engine off when the vehicle is parked or stopped for long periods of time. Drivers can also reduce petroleum consumption by avoiding the use of a remote vehicle starter and obeying no-idle zones. Fleets may implement policies to set minimum fuel-efficiency targets or require the use of idle reduction practices. In addition, fleet managers can train their drivers on the benefits of reduced idling and how to use idle reduction strategies.

For vehicles that must stop often or for extended periods of time, such as cabs, limousines, and utility trucks, the idle reduction technologies below can be implemented:

Air Heaters operate on engine fuel and are self-contained units that blow hot air directly into the vehicle’s interior. These are similar to the heaters for heavy-duty vehicles.

Coolant Heaters use the vehicle’s heat-transfer system and are mounted in the engine compartment. This technology uses the vehicle’s fuel to heat the coolant, and then pumps the heated coolant through the engine, radiator, and heater box. By keeping the engine warm, the coolant heater reduces the impact of cold starts. These are similar to the heaters for heavy-duty vehicles.

Waste-Heat Recovery Systems are similar to the energy recovery systems mentioned above for heavy-duty vehicles.

Auxiliary Power Systems are similar to the auxiliary power units mentioned above for heavy-duty vehicles.

Automatic Power Management Systems allow a vehicle driver to turn off the engine and use battery power to run the accessories from the battery. When the power management system senses the battery getting low, it restarts the engine until battery levels regenerate.

Hybridization enables vehicles requiring power take-off equipment to perform work with the main engine off.

Idling Regulations

There are many state and local laws and incentives in place to reduce idling in specific jurisdictions. For information on current idling reduction incentives and regulations, see the Clean Cities IdleBase tool and the Alternative Fuels Data Center (AFDC) Laws and Incentives database. While most current laws apply to diesel vehicles, increasingly laws are beginning to address gasoline vehicles as well.

Idle Reduction Tools

IdleBox Toolkit

The IdleBox toolkit includes resources such as print products, templates, presentations, and information resources that can assist in creating idle reduction projects for medium- and heavy-duty fleets. IdleBox can also be used to educate policymakers, fleet managers, drivers, and others about the benefits of idle reduction.

Idle Reduction Worksheets

ANL has light- and heavy-duty idle reduction worksheets for drivers and fleet managers on their Idle Reduction Tools and Outreach Materials page. The worksheets can help calculate the cost of avoidable idling, as well as potential savings from reducing idling time by implementing technologies and practices.

Additional Resources

For additional information about idling and idle reduction, please see the following resources:

The Petroleum Reduction Planning Tool can help create a plan for your fleet to reduce petroleum consumption and emissions, and includes reducing idling as one of the strategies. See the AFDC Tools page for additional resources.